Heating unit for cementing bases to electron tubes



M. R. WEINGARTEN 2,667,205 HEATING UNIT FOR CEMENTING BASES TO ELECTRON TUBES Filed Feb. 28, 195i 2 Sheeis-Sheet 1 INVENTOR MORRIS R-WE1NEARTEN ORNEY Patented Jan. 26, 1954 HEATING UNIT FOR CEMENTING BASES TO ELECTRON TUBES Morris R. Weingarten, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application February 28, 1951, Serial No. 213,134

9 Claims.

ihe present invention relates to a heating unit for cementing together parts of electrical devices with the aid of a bonding agent which is to be subjected to elevated temperatures, more particularly for cementing a base to the envelope of an electron tube such as, for example, a cathode-ray tube.

An object of the invention is to provide, in combination with means for applying heat to the parts to be cemented together, mean ensuring the correct relative positioning of said parts during the heating operation so as to enable this operation to be carried out by workers of limited skill and experience.

Another object of the invention is to provide means adapted to exert a force urging the parts into close contact with one another during the heating process, for the purpose of creating a strong and durable bond therebetween.

A further object of the invention is to provide a unit adapted to heat the parts to be bonded to a predetermined temperature at a rate calculated to avoid undesirable efiects, such as blistering, and, after maintaining said temperature for the necessary length of time, to provide a cooling action to cause the rapid hardening of the bonding agent.

Still another object of the invention is to provide means for carrying out the steps just set forth in such manner as to avoid any handling of the treated device liable to change the positioning of the parts which are being cemented.

Yet a further object of the invention is to provide a method of accurately and expeditiously cementing a base to an electron tube envelope.

The invention will be described with reference to the accompanying drawing in which:

Fig. 1 is an exploded perspective View of a heating unit representing a now preferred embodiment of the invention;

Fig. 2 is a top plan view of an assembled unit according to the invention; and

Fig. 3 illustrates use of the unit in cementing a base to the neck of a cathode-ray tube, the unit being shown in section taken on the line 3-3 of Fig. 2.

Referring to the drawing, the unit In is seen to consist, essentially, of two half shells Ha and Ill) fitting together to form a housing for a heater coil l2, a handle l3 secured to the upper half shell Ha, and a holding member concentric with said housing, this holding member comprising a ring Hi from which extend a plurality of aligning elements or guides, here shown as three fingers l5a, b, I50, which are parallel to and equidistant from the housing axis. The ring I 4 is mounted within a central aperture [6a of the upper housing portion I l a, havin a diameter greater than that of the ring so as to provide an annular clearance between the latter and memher I la, and is held in this position by mean of lugs I! which are joined (e. g. soldered) to this housing portion and are fastened to the ring M by screws IS. The fingers I5a, 15b, and I50 extend downwardly through an aperture liib in the lower housing portion Hb which is coextensive with the aperture 16a; these fingers are flared at their ends to facilitate insertion therebetween of the neck IQ of a cathode-ray tube 20 to which a resinous base 2! is to be adhesively secured.

The handle 13 is of annular configuration and is provided with depending feet 22, preferably of thermally insulating material, attached to the half shell Ha by means of screws 23. The half shells Ila and lib, fastened together by a bayonet lock comprising screws -24. on member Ha engaging slots 25 in member Hb, are preferably made of copper and may be chromium plated on the inside to form a heat reflector. Coil 12 is supported on the housing portion H?) by means of insulating posts 26 to which it is anchored with the aid of rings 21, the posts 26 being secured to this portion by screws 28. The ends of the coil l2 are engaged by terminal screws 29a, 29b passing, respectively, through insulating terminal pos ts 363a, 3817 which are recessed at the bottom to receive upstanding bosses of insulating washers 3m, 3lb, these bosses in turn ex tending through holes 32, 32b in half shell lib. Nuts 33a, 34a, and 3%, 3-42), mating with terminal screws 29a, 29b, serve to complete a conductive connection between the ends of the coil i2 and respective conductors of a power supply cable 35 leading to a suitable source of heating current (not shown). A cover 3% enc'ases the bare ends of the cable conductors and is held in position on the underside of half shell Mb by insulating heads 31a, 31b which engage the ends of the screws 29a, 2%, respectively, and have upstanding bosses extending through holes 38a, 38b of the cover 36.

The ring M has a crenelated periphery forming flutes 39 within certain of which are lodged the fingers i511, I51), and 450, being secured to the ring by means of screws 40. The bottom of the ring is recesed at 4| to afford a seat against which the base 2| may bear from below, this base being provided in conventional manner with a key-bearing boss 4| and with pins 4|" all received in the central aperture of the ring.

The operation of the unit hereinabove described is as follows:

The tube 20 is placed in inverted position, as illustrated in Fig. 3, upon some convenient support (not shown) so that its neck 19 extends upwardly. Thereupon the base 2 I, held by friction between the fingers l5a, 15b, I50, is fitted upon this neck l9 after a suitable sealing compound, which may be a thermosetting material, has been placed inside the base as indicated at 42. The ring it, having the rest of the unit I attached thereto, acts as a weight serving to press the base 21 down upon the neck H) of thetu'be. Next the heating coil [2 is energized; if the material of the base is a phenol formaldehyde condensation product such as known under the registered trade-mark Bakelite, the current through the coil I2 is preferably regulated in such manner that a temperature of 160-1'70 C. will be reached in about minutes, this gradient having been found satisfactory in that it prevents the formation of bubbles in the sealing compound due to excessive evaporation of gases. After the current has been shut off, cooling may be accelerated with the aid of a cooling fluid, such as an air stream, directed axially through the housing by way of the apertures 56a, 16b and the flutes 39;

Fig. 3 shows for this purpose a pair of pipes 43a,

432) from which streams of cold air are directed upwardly along the neck Hi to emerge within the handle 13.

Although the invention has been described and illustrated with reference to a specific embodimerit, it should be understood that the same may be realized in other forms or adapted to other uses without thereby departing from the scope of the appended claims.

What claimed is:

1. A heating unit for cementing together two parts of an electrical device, comprising a housing, heating means inside said housing, holder means on said housing forming a seat for one of said parts, and aligning means adjacent said holder means adapted to guide the other of said parts into contact with said one of said parts when seated in said holder means.

2. A heating unit for cementing together two parts of an electrical device, comprising an annular housing having a central aperture, heating means inside said housing, holder means centrall located within said aperture and forming a seat for one of said. parts, and aligning means extending axially beyond said housing from said holder means, said aligning means being adapted to guide the other of said parts into contact with said one of said parts when seated in said holder means.

3. A heating unit for cementing a base to an elongated portion of the envelope of an electron tube, comprising an annular housing having a central aperture, heating means inside said housing, a holder centrally located within said aperture and provided with a concentric recess to accommodate said base, said recess being located inside said housing, and aligning means extending axially beyond said housing from said recess, said aligning means being adapted to guide said elongated portion into contact with said base when held in said recess.

4. A heating unit for cementing a base to an elongated portion of the envelope of an electron .tube, comprising an annular, horizontally positioned housing having a central aperture, heating means inside said housing, a holder cen trally located in the upper part of said aperture and provided with a concentric bottom recess to accommodate said base, aligning means extending downwardly beyond said housing from said recess, said aligning means being adapted to guide said elongated portion upwardly into contact with said base when held in said recess, and means for directing a stream of cooling fluid through said aperture for cooling said base after a cementing operation.

5. A heating unit for cementing a base to an elongated portion of the envelope of an electron tube, comprising an upper and a lower half shell together forming a housing, said half shells being formed with substantially coextensive apertures, a ring member having an annular seat thereon centrally positioned within the aperture of but spaced from said upper half shell, a plurality of spaced fingers extending downwardly from said ring member in an array coaxial with said seat through and beyond the aperture of said lower half shell, heating means in said housing surrounding said ring member and said fingers, and mounting means securing said ring member to said upper half shell.

6. A heating unit for cementing together two parts of an electrical device, comprising an annular housing having a central opening, heating means within said housing, holder means centrally located within said opening and forming a seat for one of said parts, aligning means extending axially of and beyond said housing from said holder and adapted to guide the other of said parts into contact with said one of said parts, said holder means having a smaller area than said opening, whereby an annular space is defined between said holding means and said housing, and means for directing a stream of cooling fluid into said space, whereby said parts are cooled after cementing for quick removal from said heating unit.

7. A heating unit for cementing a base to an elongated portion of the envelope of an electron tube, comprising an annular housing having a central opening, heating means within said housing, a holder extending centrally into said opening and provided with a concentric recess disposed within said housing and adapted to receive said base, aligning means extending axially beyond said housing from said recess and adapted to guide said elongated portion into contact with said base in said recess, said opening having a larger transverse area than said holder and aligning means, whereby an air space is provided around said holder and aligning means, and means adjacent said housing for directing a cooling fluid into said space, whereby said base and elongated portions are cooled for quick removal from said unit after a cementing operation.

8. A heating unit for cementing a base to a stem portion of the envelope of an electron tube, comprising an annular structure adapted to be positioned over a loosely mounted base and stem assembly, said structure including an annular housing having a heating element therein, said housing having an axial opening of predetermined transverse area, a holding member in said housing and extending through said opening, said holding member having a relatively large mass for providing a downward force adapted to be applied to said assembly, whereby a cementing of said base to said stem is facilitated, said holder having a transverse area smaller than said predetermined area, whereby a space is provided between said holder and said housing, and means adjacent said housing for directing a stream of cooling fluid through said space for rapidly cooling said assembly after a cementing operation.

9. A heating unit for cementing a base to a stem of an electron tube, comprising an annular structure adapted to be positioned over a base loosely mounted on a stem having thermosetting cement thereon, said structure including a holder having a recess adapted to rest on said base, a chamber having spaced parallel walls having coextensive openings therein, said holder being within said housing and extending in one direction from said recess through on of said openings, a heater in said housing spaced from said recess in the opposite direction, whereby said heater is opposite a region on said base and stem to be cemented, spaced fingers extending from said holder and through the other of said openings, said holder having a smaller cross-section than said one of said openings. whereby portions of said coextensive openings are free from obstruction, and means outside said housing and,

adjacent one of said openings for directing a stream of cooling fluid through said portions for cooling said base and stem "after cementing.

MORRIS R. WEINGARTEN.

References Cited in the file of this patent UNITED STATES PATENTS Spalding June 5, 1951 

